Method of forming a polymeric foam container

ABSTRACT

An optional venting container comprises a base and a lid. The lid is releasably latched to the base. The lid comprises at least one ventable area formed therein. The at least one ventable area is adapted to form a vent only upon a user asserting pressure thereon. The lid is made from a polymeric foam.

FIELD OF INVENTION

The present invention relates generally to the packaging industry. Moreparticularly, the present invention relates to polymeric foam containerswith optional venting.

BACKGROUND OF THE INVENTION

The use of inexpensive polymeric foam containers, such as foamed alkenylaromatic polymeric containers, has become popular, especially forpreparing and serving various food products. These containers generallyhave been used for heating and storing the food product(s) disposedtherein. These containers typically comprise a cover or lid and a base.

One disadvantage of existing containers is the lack of flexibility onventing given to the end users of these containers. Some food needs tobe vented in a closed container, while other foods do not need ventingin a closed container. For example, some fried foods tend to get soggyif the generated steam cannot exit the container, while other foods willlose heat quickly if the container has vents.

The lack of flexibility in existing containers often results in storeowners purchasing both vented and non-vented polymeric foam containers.Alternatively, the store owners may be forced to vent the container byripping or puncturing it. Such ripping or puncturing often will resultin a container that is not aesthetically pleasing to the end user.

A need therefore exists for a polymeric foam container to have moreflexibility and versatility in venting for the end user.

SUMMARY OF THE INVENTION

According to one embodiment, an optional venting container comprises abase and a lid. The lid is releasably latched to the base. The lidcomprises at least one ventable area formed therein. The at least oneventable area is adapted to form a vent only upon a user assertingpressure thereon. The lid is made from a polymeric foam.

According to another embodiment, an optional venting container comprisesa base and a lid. The lid is releasably latched to the base. The lidcomprises at least one ventable area formed therein. The at least oneventable area is adapted to form a vent only upon a user assertingpressure thereon. The at least one ventable area is formed by aperforation cut. The lid is made from a polymeric foam.

According to a further embodiment, an optional venting polymeric foamcontainer comprises a base, a lid, and a hinge. The lid is releasablylatched to the base. The lid comprises at least one ventable area formedtherein. The at least one ventable area is adapted to form a vent onlyupon a user asserting pressure thereon. The at least one ventable areais formed by a perforation cut. The hinge connects the base and the lidand allows the lid to pivot with respect to the base. The base and thelid are made from the same polymeric foam.

According to one method, a polymeric foam container is formed byproviding a foamable resin in an extruder. The foamable resin is meltedin the extruder and then is extruded from the extruder to form anextruded material. The extruded material is thermoformed into acontainer comprising a base and a lid. The lid is releasably latched tothe base. The lid comprises at least one ventable area formed therein.The at least one ventable area is adapted to form a vent only upon auser asserting pressure thereon.

According to yet another embodiment, a polymeric foam lid, which isadapted to be releasably latched to a base, comprises at least oneventable area formed therein. The at least one ventable area is adaptedto form a vent only upon a user asserting pressure thereon. The lid ismade from a polymeric foam.

According to another method, a polymeric foam lid, which is adapted tobe releasably latched to a base, is formed by providing a foamable resinin an extruder. The foamable resin is melted in the extruder. Thefoamable resin is extruded from the extruder to form an extrudedmaterial. The extruded material is thermoformed into a lid. The lidcomprises at least one ventable area formed therein. The at least oneventable area is adapted to form a vent only upon a user assertingpressure thereon.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the invention will become apparent on reading thefollowing detailed description and on reference to the drawings.

FIG. 1 is a perspective view of a container according to one embodimentof the present invention;

FIG. 2 is a top view of the container of FIG. 1;

FIG. 3 is a cross-sectional view taken generally along the line 3-3 ofFIG. 2 in a closed position; and

FIG. 4 is a cross-sectional view taken generally along the line 3-3 ofFIG. 2 in a vented position.

While the invention is susceptible to various modifications andalternative forms, a specific embodiment thereof has been shown by wayof example in the drawing and will herein be described in detail. Itshould be understood, however, that it is not intended to limit theinvention to the particular form disclosed but, on the contrary, theintention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the invention as defined by theappended claims.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Referring to FIGS. 1-4, a container 10 according to one embodiment ofthe present invention is depicted. The height and shape of the containermay vary from that shown without departing from the scope of theinvention. For example, the container 10 is shown as being generallyrectangular or square, but it is contemplated that shapes like oval,circular, and other polygonal and non-polygonal shapes may be used.

The container of the present invention is typically used to hold food.The container may be used for serving, storing, preparing and/orre-heating the food such as pre-packed meals. The container of thepresent invention desirably has insulating properties to assist inmaintaining the temperature of any food contained therein. One exampleof such a container is an alkenyl aromatic polymeric foam container.

The container 10 of FIGS. 1-4 includes a base 12, a lid 14 and a hinge16. The hinge 16 connects the base 12 and the lid 14 and enables the lidto rotate relative to the base so as to open and close the container 10.The lid 14 is adapted to releasably engage the base 12. According toanother embodiment, the base and the lid may be formed from separatepieces without using a hinge. In this embodiment, the lid is alsoadapted to releasably engage the base.

The base 12 comprises a bottom 18 and a sidewall 20 that encompasses andprojects upwardly and outwardly from the bottom 18. It is contemplatedthat the sidewall may project only upwardly from the bottom. The bottomand/or sidewall may include ribs for additional carrying strength. It iscontemplated that the base may be a generally flat surface that isadapted to releasably engage the lid. In such an embodiment, the basewould not include a sidewall extending upwardly therefrom.

The base 12 may further include an optional rim (e.g., continuous rim 22in FIGS. 3 and 4) that encompasses and projects laterally outwardly fromthe sidewall 20. The optional rim may be discontinuous, although, ifused, it is preferred to be continuous. The rim is advantageous for anumber of reasons including providing supporting strength when thecontainer is being placed in the closed position. Additionally, theprocess of making the container, such as by thermoforming, is madeeasier by using a rim. Alternatively, the container may be formedwithout a rim.

The lid 14 comprises a top wall 24 and a sidewall 26 that encompassesand projects downwardly and outwardly from the top wall 24. The top wall24 is desirably elevated with respect to the cooperating base 12 toaccommodate the food products therein. The top wall 24 may include acentral portion that is recessed relative to a remainder of the top wallto cooperate with the base (like base 12) of another container stackedatop the container 10. It is contemplated that the sidewall may projectonly downwardly from the top wall. The lid 14 further includes anoptional rim 28 (see FIGS. 3 and 4) encompassing and extending upwardlyand outwardly from the sidewall 26. It is contemplated that the optionalrim may only project outwardly from the sidewall. If an optional rim isformed on the lid, it is desirable that it corresponds with an optionalrim formed on the base.

The lid 14 further comprises a plurality of ventable areas 30 formedtherein. The plurality of ventable areas 30 is shown in FIGS. 1 and 2 asbeing located in the generally corner of the lid 14 on a top wall 24thereof. The plurality of ventable areas 30 enables a user, if desired,to vent steam, pressure and/or heat caused by food 32 located in thecontainer 10 as shown in FIGS. 3 and 4. The plurality of ventable areas30 stays closed, keeping in steam, pressure and heat until the userdecides that the ventable areas should be opened to vent any steam,pressure and/or heat contained therein. Additionally, the plurality ofventable areas, when closed, functions as a protective barrier or wallto prevent or inhibit dust or other particles from entering thecontainer 10.

The plurality of ventable areas 30 does not open automatically once theinternal pressure reaches a certain point associated with the heating offoods. Thus, whether the contents of the container are vented isdetermined solely by the user. It is contemplated that the container mayhave at least one ventable area, which is formed in the lid. Thus, it iscontemplated that the lid may form exactly one ventable area.

According to one embodiment, the plurality of ventable areas 30 of FIG.2 has three sides 30 a-c that are not continuous connected. The threesides 30 a-c may be formed by a knife blade or sharpened section of toolsteel that includes at least one score therein to assist in keeping theventable area in a closed position. This is referred to herein as aperforated area. Because the at least one score is formed in one or moreof the sides 30 a-c, for example, the three sides 30 a-c are notcontinuously connected. This is shown with score 30 g in FIGS. 2 and 3.It is contemplated that each side 30 a-c may have a plurality of scoresformed therein.

The perforated areas may be moved to an open position by, for example, ahinge or crease upon a user asserting pressure thereon. For example, theuser may push downwardly on the ventable area to assert pressure to movethe ventable area to an open position. Alternatively, the user may graspthe ventable area and assert pressure to move the ventable area to anopen position.

It is contemplated that the plurality of ventable areas may be formedwith a knife cut. The knife cut may cut completely through the surfaceof the lid. In this embodiment, the plurality of ventable areas remainsgenerally closed until the user asserts pressure thereon. Thus, in aclosed position, the ventable areas retain a substantial amount, if notvirtually all, of the steam, pressure and/or heat contained therein and,thus, does not vent until the user moves the ventable area to an openposition by asserting pressure thereon. For example, the user may pushdownwardly on the ventable area to assert pressure to move the ventablearea to an open position. Alternatively, the user may grasp the ventablearea and assert pressure to move the ventable area to an open position.

It is contemplated that the knife cut may not extend completely throughthe surface of the lid. For example, the knife cut may extend at least50% into the surface so as to allow a user to move the ventable area toan open position by asserting pressure thereon. The knife cut typicallyextends at least 75% or even 90% or 95% into the surface of the lid soas to allow a user to move the ventable area to an open position byasserting pressure thereon.

The area between ends 30 d and 30 e of respective sides 30 a, 30 c mayform a hinge. The hinged area allows a respective one of the pluralityof ventable areas 30 to pivot in a manner that allows the steam,pressure and/or heat to escape from the container 10. Alternatively, thearea between ends 30 d and 30 e of respective sides 30 a, 30 c may forma crease. The crease assists in moving a respective one of the ventableareas to a vented position. It is contemplated that the plurality ofventable areas may be moved to an open position without using a hinge orcrease. A crease, however, may form after opening the ventable area.

To vent the container according to one method, a user presses downwardlyon the ventable area 30 as shown in FIG. 3, resulting in the ventablearea 30 opening and venting steam, heat and/or pressure from thecontainer 10 as shown in FIG. 4. Alternatively, a user may grasp theventable area and assert pressure thereon to move the ventable area toan open position. The ventable area 20 after being moved to a ventedposition desirably remains with the remainder of the lid. It iscontemplated that the ventable areas may be detached from the remainderof the lid during movement to the vented position.

The plurality of ventable areas may be located in different areas on thelid than depicted in FIGS. 1 and 2, including the sidewalls 26 of thelid 14 and other locations of the top wall 24 of the lid 14. It isdesirable to locate the plurality of ventable areas near or in the topwall so as to assist in preventing or inhibiting any liquid juices ofthe food product from escaping the container 10. The liquid juices, ifpresent, should remain in the container 10 as long as the container 10is not substantially tilted towards any of the plurality of ventableareas 30. It is also contemplated that if a compartmented container isused, then at least one ventable area may be located over certain foods.Thus, if a certain food in one of the compartments is the only one to bevented, then the ventable area located nearest to this compartment isopened, while the remaining ones of the ventable areas remain closed.

At least one ventable area may be located on a relative flat surfacesuch as top wall 24 to assist in preventing or inhibiting a scrapingaction similar to a shear key. This assists in forming a ventable areathat will open on pressure from the user. This also assists in makingthe cut without having to push the material out of the way. At least oneventable area may also be formed on a slight angle (such as shown inFIG. 1) to allow improved venting when the containers are stacked uponeach other. For example, this angle may be from 0 to about 45° and, morespecifically, from about 10° to about 20° relative to a parallel planeof the top of the container.

The base and the lid may be formed with one of a variety of latching orclosure mechanisms known to those skilled in the art. For example, thebase and lid may be releasably latched by a latching mechanism describedin U.S. Pat. No. 5,758,791. Releasably latched is defined herein asincluding snap engagements, firmly-held engagements and substantiallyleak-resistant engagements. It is contemplated that the container 10 ofthe present invention may be releasably latched by other known latchingmechanisms, such as that described in U.S. Pat. No. 5,607,709. It isalso contemplated that the base and the lid may be releasably latched byusing undercuts. To assist a user in disengaging the lid 14 and the base12, the lid and the base may include one or more tabs.

The plurality of ventable areas 30 of container 10 is shown as beinggenerally finger shaped or U-shaped. It is contemplated that the atleast one ventable area may be other shapes, such as a triangular shape,rectangular shape, other polygonal shapes or non-polygonal shapes. Theventable areas are desirably formed to be aesthetically pleasing to theuser in both the open and closed positions.

According to one embodiment, the lid 14 of the container 10 is made froman alkenyl aromatic polymeric foam. The term “alkenyl aromatic polymer”as used herein includes polymers of aromatic hydrocarbon molecules thatcontain an aryl group joined to an olefinic group with only double bondsin the linear structure, such as styrene, α-methylstyrene,o-methylstyrene, m-methylstyrene, p-methylstyrene, α-ethylstyrene,α-vinylxylene, α-chlorostyrene, α-bromostyrene, and vinyl toluene.Alkenyl aromatic polymers also include homopolymers of styrene (commonlyreferred to as polystyrene), copolymers of styrene and butadiene, andrubber-toughened polystyrene (commonly referred to as high impactpolystyrene or HIPS). The alkenyl aromatic polymer may be an orientedpolystyrene (OPS). The lid may be made from more than one alkenylaromatic polymer.

The lid of the container may also be formed from foams comprisingpolyolefins such as polypropylene, polyesters such as polyethyleneterephthalate (PET), and combinations thereof. The polymeric foam lidmay be made from a mineral-filled polymeric material such as, forexample, talc or calcium carbonate-filled polyolefin.

The base 12 of the container 10 may be made of the same materialsdescribed above in forming the lid 14. Specifically, the base 12 may beformed of alkenyl aromatic polymeric foams, polyolefins foams such aspolypropylene, polyesters foams such as polyethylene terephthalate(PET), and combinations thereof. The base may be made from amineral-filled polymeric material such as, for example, talc or calciumcarbonate-filled polyolefin. It is also contemplated that the base maybe formed of other non-foamed materials such as, for example, aluminum,paper and non-foamed polymeric materials, such as polyolefins andpolyesters.

The containers of the present invention are typically disposable, but itis contemplated that they may be reused at a future time. It iscontemplated that the containers may be formed of multiple compartments.Such containers are desirable for placing food items in differentcompartments to prevent or inhibit commingling of items. Undesirablemixing of food items can corrupt the flavor and the consistency of thefood items. The thickness of the container generally ranges from about30 to about 150 mils, but is typically from about 70 to about 100 mils.

A method of using such a container includes placing the food therein,venting the container by opening at least one ventable area such asshown in FIGS. 3 and 4. The container may then be placed in a heatingapparatus, such as a microwave, to heat the food. The container maycontain solid food products. The container may be used for storage inthe refrigerator and/or the freezer.

The polymeric foam container may be formed using conventionalthermoforming (e.g., by pressure, vacuum or the combination thereof).According to one method of thermoforming, polymeric pellets such as analkenyl aromatic polymer resin and additives, if any, are added into anextruder. The pellets of the alkenyl aromatic polymeric resin andadditives, if any, are melted to form a blend. The blend is extrudedthrough a die to form an extruded foamed sheet. The extruded foamedsheet is thermoformed to a desired shape of a container.

According to this method, the container is made in a thermoforming mold.The mold includes a knife blade or sharpened section of tool materialthat is located to form the at least one ventable area. The knife blademay be serrated. The knife blade or sharpened section of tool materialmay be made of material such as steel. It is contemplated that othermaterials may be used in forming the knife blade or sharpened section oftool material. The at least one ventable area may be formed in atrimming step of the process.

The knife blade or sharpened section of tool material is positioned toform the desired shape of the ventable areas. To assist in allowing theventable areas to remain closed until opened by the user, there may beat least one score in the knife or sharpened section of tool material toform a perforated cut. To maintain the sharpness of the knife orsharpened section of tool material, the contact area below it may havesome cushion while still ensuring reliable contact. This contact areamay be a striker plate that assists in aligning the knife blade orsharpened section of tool material to assist in properly locating the atleast one ventable area. To assist in replacing of worn or spenttooling, the striker plate and the knife blade or sharpened section oftool material are often made of materials with different hardness. Forexample, the striker plate may be made of a harder material than theknife blade or sharpened section of tool material such that the knifeblade or sharpened section of tool material will be replaced more oftenthan the striker plate.

While the present invention has been described with reference to one ormore particular embodiments, those skilled in the art will recognizethat many changes may be made thereto without departing from the spiritand scope of the present invention. Each of these embodiments andobvious variations thereof is contemplated as falling within the spiritand scope of the claimed invention, which is set forth in the followingclaims.

1. A method of forming a polymeric foam container comprising: providinga foamable resin in an extruder; extruding the foamable resin from theextruder to form an extruded material; thermoforming the extrudedmaterial into a container including a base and a lid releasably latchedto the base, the lid including at least one ventable area formedtherein, the at least one ventable area having a perimeter defined by adiscontinuous cut consisting of a discontinuity between opposing ends ofthe discontinuous cut, the opposing ends defining a hinge portiontherebetween and the discontinuity spaced substantially from the hingeportion to form a single frangible portion.
 2. The method of claim 1,wherein the at least one ventable area is formed while trimming excessmaterial from the polymeric container.
 3. The method of claim 1, whereinthe discontinuous cut is formed with a sharpened tool having at leastone score therein to define the discontinuity therein.
 4. The method ofclaim 3, further including providing a contact area to locate the atleast one ventable area and receive the sharpened tool.
 5. The method ofclaim 4, wherein the contact area is a striker plate formed of amaterial having a hardness different than the sharpened tool.
 6. Themethod of claim 1, wherein the at least one ventable area is formed by aknife cut.
 7. The method of claim 1, wherein the container are formedfrom the group consisting of alkenyl aromatic polymeric foams,polyolefins foams, polyesters foams, and combinations thereof.
 8. Themethod of claim 1, wherein the container has a thickness of about 20 toabout 150 mils.
 9. A method of venting a polymeric container comprising:providing a polymeric container including a base and a lid releasablylatched to the base, the lid including at least one ventable area formedtherein, the at least one ventable area having a perimeter defined by adiscontinuous cut consisting of a discontinuity between opposing ends ofthe discontinuous cut, the opposing ends defining a hinge portiontherebetween and the discontinuity spaced substantially from the hingeportion to form a single frangible portion; and rupturing the singlefrangible portion of the at least one ventable area to move the at leastone ventable area toward an open position.
 10. The method of claim 9,wherein the lid includes a sidewall and a top wall, the sidewallencompasses and extends generally downward from the top wall, the topwall has an angled surface located near the intersection of the top walland the sidewall.
 11. The method of claim 10, wherein the at least oneventable area is formed in the angled surface of the top wall.
 12. Themethod of claim 9, wherein the at least one ventable area includes afirst side and a third side with a second side disposed therebetween.13. The method of claim 12, wherein the hinge is disposed opposite thesecond side and at the termination of the first and third side.
 14. Themethod of claim 13, wherein the single frangible portion is disposedopposite the hinge.
 15. The method of claim 9, wherein the at least oneventable area is generally U-shaped.
 16. The method of claim 9, whereinthe lid forms a plurality of ventable areas.
 17. The method of claim 9,further including the at least one ventable area remains attached to thelid in the open position.
 18. The method of claim 9, wherein a creaseforms in the lid after the at least one ventable area is moved to theopen position.
 19. The method of claim 9, wherein the base comprises abottom, a sidewall and a first rim, the sidewall encompasses the bottomand extends upwardly from the bottom, the first rim encompasses thesidewall and extends generally outwardly therefrom.
 20. The method ofclaim 19, wherein the lid further includes a second rim, a secondsidewall and a top wall, the second sidewall encompasses and extendsgenerally downward from the top wall, the second rim extends generallyoutwardly from the second sidewall, the second rim of the lid is adaptedto releasably latch with the first rim of the base.